


Oxygen

by 7PercentSolution



Series: Periodic Tales [3]
Category: Sherlock (TV)
Genre: Angst, Chemistry, Kidlock
Language: English
Status: Completed
Published: 2016-07-09
Updated: 2016-07-09
Packaged: 2018-07-22 13:36:34
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 3
Words: 5,563
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7441219
Author URL: https://archiveofourown.org/users/7PercentSolution/pseuds/7PercentSolution
Summary: <blockquote class="userstuff">
              <p>Oxygen O 15.9994</p><p>The eighth element on the Periodic Table. Discovered in 1773 in Sweden and 1774 in Wiltshire. The third most abundant element in the universe and the most abundant element in the Earth's crust, as well as in the human body. Essential for almost all forms of life on Earth, it is also highly flammable. It sustains combustion and, under pressure, can be explosive.</p>
            </blockquote>





	1. Chapter 1

**Part One:**

**O(1 ) Atomic Oxygen – a free radical, which when generated in excess or not appropriately controlled can wreak havoc on a broad range of macromolecules. With extremely high chemical reactivity, it drives not only normal biological activities, but can inflict damage on cells.**

* * *

There was another kind of experiment that told John the depths of boredom, ennui and frustration into which Sherlock had fallen. Most, but not all of these, involved something explosive. Within a month of moving into Baker Street he'd bought new fire extinguishers and installed a smoke alarm.

He was upstairs getting dressed after a shower the first time the alarm went off. The noise was deafening, and Sherlock's shouting didn't help either. Mind you, for someone who was hypersensitive, at least Sherlock wasn't curled up in a ball in a corner with his hands over his ears. John managed to talk Sherlock off the kitchen table where he was standing trying to rip it out of the ceiling. John then got the ladder and pulled the battery out.

"That is the invention of the devil, John, and you will remove it immediately." Sherlock was almost panting, quite near to a meltdown.

"I can't do that, Sherlock, if you insist on trying to burn things and cause explosions in our kitchen."

But John did move the smoke alarm to the living room ceiling over the sofa, to give a little more leeway. He did buy another, larger fire extinguisher for the kitchen, and a fire blanket.

Today was the ninth day without a case. Mycroft often worried about 'danger nights', when Sherlock might be having issues, but in John's experience, he worried more about days like these. He could live with mad scientist, but bad scientist was...scary.

Sherlock had cleared the kitchen table of glassware and the usual jumble of kit. There was a small tin of something called Danish Oil, a rag and a canister of something John recognised as O+, which had been advertised recently on the TV as "recreational Oxygen" to "restore, revive, refresh- no calories, no carbs, no caffeine, no crash". His forehead creased. What the hell did Sherlock have in mind?

"Relax, John. Oxygen does not burn."

"Then why are you planning to start a fire with it?"

"I'm not. Oxygen, however, is needed for other things to burn. I am attempting to discover at what concentration level a mixture of oxygen and this oil will spontaneously ignite."

"Why?"

"Why not?" The glower that accompanied this very rhetorical question made it clear that any interference from John would be resisted.

oOo

"Ow!" The boy dropped the burning match. He had stolen the box of matches from the gardener who had left them in the pocket of his jacket, on the nail in the potting shed. Sherlock was hiding now in a lean-to that was attached to the mower shed. He was trying to light a candle so he could continue to read his biology book, but the wick was broken or damp, and the match had burned down to his fingers before it could catch.

The lean-to was a strange place, full of tins of odd smelling chemicals, pesticides, oils for the machinery, wood stains for the garden furniture. Sherlock recognised some of them- the fertiliser that his mother used for her tomatoes was in a bright red plastic bottle that had faded with age. He had not eaten a home-grown tomato this year. Mummy had been ill with flu in the spring, and then again in August, so she'd given up the vegetable gardening, resorting instead to just issuing instructions about the flower beds and the lawns.

"Keep James company, Sherlock; I need to rest for a while."

He didn't like James. The young gardener had no time for Sherlock. He just ignored the nine year old boy. "Piss off, will ya? I have work to do." His mother always tried to involve him in the process and would explain what she was doing as she worked. "The compost we made last year is now just the right thing for mulching. It keeps the weeds down and ensures the soil underneath doesn't dry out too much. Plants do best when they are kept just moist- not too much rain, and no prolonged drought."

He enjoyed the sound of her talking. He always listened, even if he rarely responded. He liked watching the bees and the other insects come to the flowers. He would ask the occasional question, like when she put a handful of brown powder under the roses. It came from a box with the words _blood_ ,  _fish_  and  _bone_  on it. "Why are you putting it on the bush, Mummy? Plants are not carnivores."

He'd just learned about the different types of animal species, and was trying to figure out a puzzle his mummy had set him. "There is one class of mammal on the estate that is a true omnivore. You have until Saturday to figure it out." He'd spent lots of time watching the horses, actually tried to feed one a dog biscuit, but it had turned away. Nor could he interest the barn cats in left over vegetables. They drank milk, though, and that led him to read about whether dairy products were meat or vegetables. The answer, "neither" perplexed him. Did that make mammals into carnivores, herbivores and milkivores? No, apparently lots of mammals consume milk when they are babies, so that didn't count. The ducks would take bread, but not the salami that he'd put in his pocket when no one was looking when he ate lunch at the kitchen table with Mrs Walters, the housekeeper. The nearest he'd got was with the gamekeeper's dogs. They would eat pretty much anything, being Labradors, although one spat out an olive. The other one ate it, and Sherlock wondered what that meant, when a sample of two did the opposite from one another. But the Spaniels were more fussy, and ignored the vegetables. He'd looked it up in the encyclopaedia and discovered that dogs were classed as carnivores, but were opportunistic when fed something else. So, not the right answer.

Things were boring up at the house. His father had telephoned to say he wouldn't be home that night. That cheered up Sherlock immensely, but his mother had just sighed. "Right, Walters. I'm going to have an early night then. Just send a tray up to my room, could you?" When the housekeeper left, Mummy turned to Sherlock and ruffled his hair. She was the only one he let do that. He held his right hand out, fingers extended, and she put her larger hand to his so that their fingertips touched briefly. It was Sherlock's version of a hug. He didn't like to be held ( _Too much touch, Mummy_ ) so they had evolved this way of showing affection. "Try to stay out of mischief, young man. I hope to feel better in the morning and we can tackle that iris bed. The perennials need dividing, and now's the right time to do it, before autumn frosts start."

He smiled at her, and went to get his biology book. He needed more research about what an omnivore might be. When Mrs Walters came up at nine o'clock, she told him to get ready for bed. "You need to  _try_  to sleep, Sherlock, so put the book away until tomorrow."

He wasn't ready to stop, but he knew that creating a fuss would bother everyone. So, he did as he was told, waited for her to turn off the light, and then promptly got out of bed, dressed again and then snuck out the back stairs with his book in his hand. He'd done it many times before that summer, and was accomplished at staying out all night, if it suited him. He often wandered the estate in the dark, and knew the grounds better than the gamekeeper or the estate manager. He knew where the badger setts were, where the vixen had her pups last spring- and where to get lost when Father was looking for him.

Tonight, however, he wanted to read, so he took his torch with him. When he got to the lean-to, he opened the padlock- it was really easy to guess the numbers having watched James yesterday put some paraffin back in it.

He'd read four more pages when his torch went out. He shook the batteries in the hope of getting some more power, but it stayed dark. That's when he remembered the box of matches. James was a smoker.

So, when the wick wouldn't light and he dropped the match, he expected it would go out. When it landed on a rag, however, it suddenly burst into flame.  _Why did that happen? Cloth doesn't burn as quickly as that; it smoulders first._  Mycroft had given him a chemistry set last Christmas, and he'd learned a lot about what burned and what didn't- always under Mummy's watchful eye. She only let him use the burner when she was there, and he had learned why.

So, this surprised him. He looked around the lean-to in the brighter light- and spotted a cloth.  _Like a fire-blanket_ \- cut off the air and the fire will go out. It was basic chemistry that his mother had taught him when he first got the kit- she put the tube with the fire blanket on the wall, and showed him how to use it.

So, he took the cloth and tried to smother the fire. But, it didn't go out; instead the cloth caught fire and suddenly the place was hot and smoky and very bright, and very scary. He picked up his book and ran out. When he got up to the house he just went back up the stairs, changed back into his pyjamas and went to bed, clutching his book to his chest.

The next morning, the gardener was fired. "You have no excuse, James- leaving oil soaked rags in the shed. What were you thinking? You know that Danish oil impregnated cloth needs to be kept in an airtight container, or it will spontaneously ignite. We've just lost the tractor lawn mower as a result of your carelessness."

On Saturday, Sherlock told his mother the answer to the puzzle. "It's people, isn't it? Humans are omnivores. We eat meat and vegetables and milk."

She reached her hand out and their fingers touched. "Yes, Sherlock. You're a clever boy." He didn't reply, and spent most of the rest of the afternoon trying to figure out how the cloth might have ignited on its own. If he could figure that out, he'd feel happier.


	2. Chapter 2

**Part Two:   Dioxygen- O(2), the most abundant form of oxygen in the earth's atmosphere. Too much or too little of this form of atmospheric oxygen can have serious medical consequences. A lack of oxygen, called hypoperfusion to an area of the brain can lead to expressive aphasia, the inability to use speech to communicate.**

* * *

" _Any inflammable substance in the form of a gas, a liquid, or a fine dust can explode when mixed with air. If smouldering wood is placed in pure oxygen, it will combine with the oxygen so fast that it will become hot enough to burst into flame again."_  Barbara Lowery had moved on in the book now to the element, oxygen. She'd never studied chemistry at school; she'd done biology. Despite the fact that the book seemed to be aimed at teenagers rather than a developmentally challenged boy, she was finding the book quite interesting. It was not just factual but it explained things that she wasn't sure she'd ever been taught. For example, helium was an inert gas- it didn't join with other elements. She laughed when she read the next bit: " _Some people seem to think there is something aristocratic about this aloofness. For that reason, the group is sometimes called the noble gases."_

Sherlock looked up at the sound of her laughter, curious. He was starting to accept her presence. No eye contact yet. She glanced down at her watch.  _Oops- it's nearly six o'clock; got to get going._

"Sherlock, I need to get back to work now. We'll have to pick this up later. Maybe one of the nurses on the next shift will read to you."

The boy just reached his hands up, not looking at her, but off over her shoulder. His face was impassive, but she knew what he wanted. She handed over the book, and he opened it. But, this time, instead of resuming where she left off, he flicked back through the pages to Hydrogen and began to read. "Why are you re-reading that bit, Sherlock?"

There was no reply, or even recognition that she had spoken. She sighed.

According to the junior doctor she handed over to each morning, the ten year old had been making considerable strides in communication skills before his mother's death, but the loss of the person to whom he had emotionally attached had derailed that progress completely. He had not spoken once in the entire four and half months that he'd been at the hospital.

 _Is there no other family then?_  Perhaps Dr Molhotra would know. It was a sad part of her role as a night nurse that she rarely ever met the patients' families or got to know their background. The child seemed so …alone.

The young doctor frowned. "A father who has never visited and I think an older brother, but I'm not aware that he's been to see the patient- I think he's away at university or something."

"Sherlock seemed very quiet tonight- in fact slept through until five o'clock, which he's not done since I've been here. Is he on a new drug regime?"

"No, nothing new in terms of drugs." He scanned down the chart. "Oh, he had an ECT session yesterday afternoon. That tends to put people to sleep for about ten to twelve hours minimum."

Her face must have betrayed her surprise. "I thought that ECT was no longer used with children."

"Yes, it's never been used much, but it was a bit more common a decade ago than it is now. I have to say it seems a pretty extreme therapy, but all the protocols have been followed. The patient can't make informed consent, but the parent actually asked for it."

One of Barbara's previous jobs had been in a psychiatric ward in York. Some of the adults with schizophrenia or severe depression had been treated with a course of ECT. She'd been surprised at its effects. Pulsing a high voltage electrical current through someone's brain had always seemed to her a rather drastic measure. She'd seen adults wake up from such sessions disorientated, confused and with significant memory loss. She wondered what effect it could be having on the ten year old. Perhaps that was why he was re-reading sections of his book.  _Maybe he's trying to remember what the ECT made him forget?_

oOo

"Sherlock, you always say that you delete stuff that isn't important to…keep on your hard drive, but I really can't understand how you could forget that smoke inhalation is dangerous." He'd arrived at the scene about twenty minutes after Sherlock had texted him, but it still wasn't quick enough to stop the consulting detective from chasing the suspect into the burning building. When the Bulgarian car mechanic was overcome by the smoke, Sherlock dragged him out of the back door into the waiting arms of Lestrade's team. The firemen were now dousing the burning garage, which was full of odd barrels of industrial chemicals. They had been evacuated to a safe distance, and the suspect rushed off to hospital in the first ambulance on the scene. It had been Lestrade who called the second ambulance, worrying about Sherlock, but he gladly handed the task of getting the detective to accept medical treatment over to John, as soon as the doctor got there.

His flatmate was now sitting on the back of the second ambulance, not really wanting to be there, but not well enough to stand up and stalk away. The paramedic placed the oxygen mask onto Sherlock's mouth and nose, pulling the straps tight so the oxygen would maintain its pressure and high flow. The pulse oximeter was clipped to his finger, and Sherlock stared at it as if insulted by its presence.

He tried to speak but the mask muffled his words. "I'm fine."

John put his hands on his hips. "Sherlock, you don't know whether you're 'fine'; the effects of carbon monoxide poisoning are not at all clear at the start. We're going to the hospital to get you checked out. At the very least, you could have burned your throat, your bronchi- when they start to swell, you'll go into respiratory distress. Without proper level of oxygen in your blood, you could go into cardiac arrest." He snapped. "Knowing you, you'll be still saying you're fine when the paramedics say you're coding."

He literally shoved Sherlock into the back of the ambulance and the paramedic slammed the door shut before the brunet had a chance to recover his balance. When they got to the hospital, the doctor explained to the Emergency Department team what had happened. Sherlock pulled the mask off and said, "It's unlikely that I've been exposed, John. No sign of my skin turning pink."

"You know as well as I do that skin discoloration is only one symptom and it doesn't always appear. Carbon monoxide poisoning is  _serious_."

"I know that. The brain and heart are damaged when carboxyhemoglobin (COHb) levels exceed 20%. That's because the affinity of haemoglobin for CO is over 210 times higher than for O2. CO easily displaces oxygen from haemoglobin and binds to intracellular myoglobin in the myocardium. This negatively affects the oxidative phosphorylation and consequently, the energy source of heart muscle."

The Emergency Department doctor listened to the chemistry lesson and smiled. "Well, there's no sign of hypoxia affecting either his lung capacity or his brain function if he can get through all that on one breath."

But just to be sure, he ordered that Sherlock should be tested for the COHb levels, and given a blood glucose test, a cardiac enzymes test plus an ECG to see that nothing was amiss. And, despite the consulting detective's protests, when the results came back showing evidence of mild exposure to carbon monoxide, he also ordered an overnight stay in the hospital, so Sherlock could be monitored should any headaches, nausea, arrhythmias or chest pain occur, due to myocardial ischemia. And he was to keep the oxygen mask on, too, to accelerate the removal of the CO.

John just told him to shut up and stop whinging. "So do as the doctor says, for once, Sherlock. You know that chemistry doesn't lie. Breathing is definitely  _NOT_ boring."


	3. Chapter 3

**Ozone- O(3) a reactive allotrope of oxygen that is very destructive and damaging, with a strong scent. Yet ozone is formed in the human body by white blood cells, and plays a part in the immune system.  When ozone breaks down to dioxygen in the body it gives rise to oxygen free radicals, which are highly reactive and capable of damaging many organic molecules. Moreover, it is believed that the powerful oxidizing properties of ozone may be a contributing factor of inflammation.**

* * *

"Why can't I see him?" Mycroft had just arrived home for the Easter Break, three weeks away from the academic hot-house of Balliol. He'd enjoyed the second term content and its focus on current UK politics; it gave him a chance to focus on something other than the gaping hole left by his grief. His mother had died one week after the new term had started, but he had permission to delay his return to Oxford until after the funeral. He'd caught up easily enough, but the demands of doing so meant he had little time to think about things he'd rather not think about.

His father was standing at the fireplace in his study. He was a tall, imposing figure; his face betrayed absolutely no emotion at all. He turned his dark blue eyes on his elder son and heir, who had inherited the Viscount title on his mother's death. "Because there is no point, Mycroft. No purpose would be served for either of you."

"I don't understand why you won't even tell me where he is."

"Because then some sentimental weakness might lead you to think you should go see him or try to communicate."

 _Yes, well- he is my little brother._ Mycroft was trying to hold his temper, but finding it hard in the face of his father's implacable refusal. "Family loyalty is not a weakness, father."

"In his case, it is. There is nothing you can do. He was born defective. He can't be held responsible for that, but there is no need for  _you_  to feel obliged in some way. I won't have him hold you back. You have more important things to think about, young man. He's where he can be cared for, by people who are specialists in dealing with people like him. That's all you need to know. This family has done its duty; time to move on."

"Mother would be …distressed by your treatment of Sherlock."

Playing that particular card was a mistake, as Mycroft realised when his father's face contorted in anger and he crossed the space between them. Now looking down into his son's eyes, Richard Holmes said very quietly, "You will not take that tone with me, young man. Caring is not an advantage. It's because of him that she neglected her own health. I should have made her send him away years ago. If I had, she might still be alive."

Mycroft stood his ground. His own anger drove the reply, "Pancreatic cancer is highly lethal, Father. She was unlikely to survive it, with or without Sherlock. You're not being fair."

"Fair?" The older man's sneer was evident. "What's fair about a wife spending all of her time with a retarded child? What's fair about that parasite sucking all the life and energy out of her? Life isn't fair, Mycroft. I would have thought you'd have figured that out by now."

 _In for a penny, in for a pound._  He took a deep breath. "I have figured out that the distance between you and mother was not all one sided. Your infidelities helped."

He could feel the barely supressed rage, and watched his father's right fist clench.  _Are you going to hit me, the way you do Sherlock? That would be new for you and me, but perhaps it's only fair._

"You have no idea what you are talking about."

Mycroft tilted his head and looked puzzled. "Don't I? Ever since that memorable occasion at the dinner table when Sherlock outed your relationship with…what was her name? Ah yes, Sharon Williams, your marketing director…I know there have been others. Mother knew, too."

The anger burned incandescent in his father's eyes. "Maybe when you are older, have a family of your own, you will realise that it takes two, Mycroft. When one partner in a marriage is totally consumed by a child's needs, the other is often driven to find company and comfort elsewhere."

Richard Holmes turned back to his desk. "Now, that is enough of this conversation. I won't dignify it by wasting any more breath. Oxygen just feeds a fire. So, there will be no further talk about the boy. He's gone. And you need to focus on your studies."

But Mycroft couldn't let go; he just couldn't. When his father made him return to university a week after the funeral, Sherlock had just been sedated by the family doctor. He couldn't say goodbye because his brother was finally asleep after almost a week of continuous crying. The boy hadn't eaten or slept, wouldn't tolerate being touched and had stopped speaking. As much pain as Mycroft felt about his mother's death, leaving his brother in such a state was almost worse.  _At least her suffering is over._  He'd called home the day after getting back to Oxford, and been told by the housekeeper that his father was away "indefinitely" on a business trip. Sherlock had been moved to a clinic, where he could be cared for. She didn't know where, because she hadn't been told.

So he faced his father now, and asked the question that had nagged at him the whole of the academic term. "You mean him to stay institutionalised -what, forever?" He sounded incredulous.

"It's not your concern. You are to focus on university, young man. You have a future. He doesn't."

It was as if there had been an electrical discharge; the air tingled. Mycroft couldn't bear to be in the same room with his father any longer. The stench of the man's prejudice was toxic. Without a word, he just turned and left. He went upstairs, packed his bag and called down to the chauffeur. "I need a lift to the train station, Michaels. Could we leave right now?" He didn't say goodbye to his father.

oOo

John surveyed the devastation. The flat was normally shambolic, chaotic and untidy, but the living room now looked like a tornado had swept through. Books were thrown off the shelves, piles of papers kicked over, whatever was on the dining table when he left was now the floor, including Sherlock's laptop. It was still on, half open, so John started by picking it up and closing it properly.

He looked over at Sherlock, who was sitting – well, not actually sitting- in the chrome and leather chair by the fireplace. The tall brunet's knees were drawn up to his chest, one of his long arms wrapped around them, and his head buried in the space between his legs and torso. All John could see of his head was the mass of dark hair, looking even more unruly and dishevelled than normal. Sherlock was a picture of misery.

"It's not your fault, Sherlock. He was intent on killing his children, no matter when we got to him. He'd timed it all out. Getting there any sooner would have just made him do it quicker."

The case had been horrible. An estranged husband kidnapped his own children- a son and daughter- because the wife wouldn't allow visitation rights. She'd applied for a court order to keep her husband away, but the police were not always around, and she'd never anticipated such extreme steps by the man she married. That his schizophrenia wasn't diagnosed didn't matter. She was hysterical with fear when a child's ear was delivered in a box through the post. She came with it to Baker Street and begged them to take the case.

Sherlock proved it wasn't from the son or daughter even faster than a DNA test- "Ear shapes, John, are unique. Look at the photos supplied by the wife. The antihelix, helix and concha for both of her children are different from the sample supplied."

"But where would he get an ear- a fresh ear at that?"

"Now you are  _finally_  asking the right question!"

After a number of false starts at hospital morgues and funeral homes, Sherlock eventually found the answer- a crematorium- and tracked down which one in a matter of hours. A visit indicated that there'd been a break-in several nights previously, but "nothing was stolen apart from some embalming fluid, so we just assumed it was kids doing a bit of thieving to pump up their marijuana smoking."

That had seemed a dead-end (no pun intended), until Sherlock deduced a link between the crematorium and the husband, whose mother had been cremated there four years before. John and he eventually found the care home where the woman had died- now closed. They arrived at the abandoned building, and searched it with a police team. After twenty minutes, they found them in the attic. The two children's bodies were still warm; their father unconscious, but he died before the ambulance arrived. The note attached to the man's coat was blunt. "They are my children and I won't let you have them."

"I should have  _known_ , John. We wasted time looking at morgues and funeral homes, when it was obvious that the man would want to cover his tracks. He simply removed an ear from a body due to be cremated the next morning. Pull the girl's hair down over where the ear had been, and there'd be no reason for the crematorium attendant to stop. The body is burned, and combustion removes all evidence."

When they returned to the flat, Sherlock disappeared into his bedroom and didn't emerge until the following morning. He was terse and tense, but when John was called by the clinic and asked to come in for a few hours to cover for an illness, the brunet waved him off. "Go, at least one of us should be useful today."

When he got back, it was to the ruins of Sherlock's rage about his failure.

"Sherlock?" John's voice was gentle, but insistent. "Please, look at me." He was worried about the total lack of response. Was this the aftermath of a meltdown?  _Yeah, what else? And I was stupid enough to leave him alone._  He glanced into the kitchen and saw the devastation of broken glass. Sherlock's experimental kit lay in shards and splinters. The microscope was on its side under the table. That's when the doctor's nose detected a scent that was an occupational hazard for a medical professional- the metallic tang of freshly oxygenated blood.

"Sherlock, what have you done to yourself?" This was more insistent, not as gentle. Looking at the brunet in the chair, John realised that he'd tucked his right hand in-between his knees and his body. "Have you hurt your hand? Let me see."

There was no response. He knew Sherlock loathed being touched, but needs must. He put a hand on the man's shoulder, and when there was no flinch or reaction, he then reached in to try and pull Sherlock's right hand free. He couldn't see it, but knew by the wet touch that he'd found the source of the scent; the hand he grasped was slick with blood. It's a unique texture- warm, wet, and yet with a viscosity distinctively different from plain water.

He pulled the hand out and grimaced at the sight. Sherlock's palm had a jagged gash, about the size of a fifty pence piece, right in the middle. It was very deep and it was bleeding heavily. The front of his pyjamas, now visible to John for the first time since he arrived, showed that the bleeding had gone on for some time.

Sherlock was strangely passive. He let John check for tendon damage, clean and suture the wound, and sat absolutely still through the whole procedure, unmoved and unmoving. He had not lifted his head to make eye contact once since John had arrived. But he didn't stop John from seeing to the injury, and when it was done and bandaged, John got him a glass of water.

"You are lucky that I came home when I did, otherwise you would probably need a transfusion. Drink it, Sherlock. You need to replace the fluids."

Awkward with his left hand, Sherlock complied obediently, and then held the empty glass in front of him, eying it with a strange expression on his face. His grip started to tighten around the glass, as if testing to see when it would break under the pressure. John quickly snatched it from his hand.

"You want to break glass. Why?"

He didn't really expect an answer, so was surprised when he got one. "It puts the fire out."

The doctor's head tilted as he scrutinised his friend. The tone of voice was utterly flat and quiet. There was no evidence of a fire in the flat, nor that there had been one. No charred scent, no smoke alarm, no fire extinguisher residue. "What fire?"

Sherlock blinked. "When I get so angry that I can't control it, then smashing glass works. The noise, the…sensation, the pain- it removes the oxygen feeding the fire in my brain. It just …goes out."

"It also results in blood and destruction, Sherlock. Can't you see that?"

Sherlock glared at him. "Save the sanctimonious preaching, John. Surely you were awake in med school when they covered NSSI. Non-Suicidal Self Injury- it's not rocket science; it's amygdala activation and stimulation of the limbic circuitry. Think of what I do as a form of self-medication. I am using the glass breaking as a form of conditioned neural stimulation. Believe me, the consequences are far less damaging than letting the fire rage unchecked."

John rolled his eyes at his friend's explanation. In one sense, he was glad for the sarcasm and cutting edge to Sherlock's explanation. Sarky he could deal with; silence was more worrying. Looking up at the ceiling, the little red light on the smoke alarm up there caught his attention.

"Sherlock, next time you feel that self-combustion is a possibility, give me a warning of some kind. I'll hang around and make sure that you don't have to resort to such drastic measures."


End file.
